Method of making moldable lignocellulosic material and product thereof



Patented June 24, 1941 I UNITED STAT MErnop OF MAKING Momma mono.-

CELLULOSIC MATERIAL AND rnoouo'r THEREOF Arlie W. Schorger, Madison,Wis., assignor to Burgess Cellulose Company, corporation of DelawareApplication August'zs, 1939, Serial No. 292,075

13 Claims.

No Drawing.

This invention relates to improved methods for treating naturallignocellulosic material, such as sawdust, corncobs, bagasse, etc., soas to render it suitable for hot-molding into hard, thermoplastic,resin-like products. The invention also relates to the products producedby such methods.

It is an object of the invention to provide improved methods for makingsuch plastic lignocellulose products, which methods are economical andresult in products having improved-plastic flow and strength.

In my co-pending joint application Serial No. 134,272, filed April 1,1937, now Patent No. 2,- 196,277, a method is disclosed in which acomminuted natural lignocelluloslc material, such as wood, corncobs,straw, bagasse, cornstalks, etc, is cooked with water at 50 to 205pounds per, square inch gauge pressure (148 C. to 200 C.) for from /2 to3 hours, and the cooked product washed with water and dried and thenmixed with from approximately 1% to 10% of aniline. A product isobtained which molds readily at temperatures of 100 C. to over 200 C.and pressures of 1600 to 5000 pounds per square inch into a hard,structureless, glossy resin-like product.

In accordance with the present invention,- it has been discovered thatdecidedly superior results are obtained if the cooked lignocelluloseafter being washed and dried is heated with the added aniline atelevated temperatures, from 100 to 225 0., prior to molding. Theanilinein an amount approximately from 1% to 15% based on the weight ofthe dry lignocellulose, is thoroughly mixed with the lignocellulose, andthe mixture heated in a closed container, preferably at 170 C. Thisheating of the mixture prior to the molding operation functions to fixthe aniline upon the lignocellulos whereby little or none of it is lostby evaporation during the sulphate and the mixture heated at 170 C. fori one hour, the aniline is fixed completely. suitable catalysts are theoxides and salts of the metals vanadium, chromium, manganese, iron,cobalt, nickel and copper.

The time and temperature employed in the fixing operation de- Freeport,11]., a"

pends upon the amount of aniline used. As the amount of aniline isincreased, the time, or the temperature, .or both should be increased toobtain complete fixation. It is obvious that such fixation results ingreat economy of operation and the maximum utilization of the aniline.

It is customary to add small amounts of a metallic stearate, such aszinc stearate. to the plastic lignocellulosic material to prevent itssticking to the mold. In accordance with the present invention, therelease-promoting agent is caused to serve the function of a catalystalso, by employing a stearate of a metal mentioned heretofore, such ascopper stearate: As a speciflc example, 1% of copper stearate, based onthe weight of the lignocellulosic material, is dissolved in the anilineand the solution is added to the dried lignocellulosic material and themixture is heated in a rotating digester.

The resulting ilgnocellulose-aniline compound possesses improvedthermoplastici-ty and may be molded readily under heat and pressure toproduce hard, resin-like, water-resistant products. The water resistanceis increased materially over that of prior lignocellulose plastics ofthis character. A suitable plasticizer, such as water, aniline,furfural, or a phenol, may be admixed with the lignocellulose-anilinecompound prior to the molding operation. Up to 10% of the plasticizer,based on the weight of the lignocellulose, usually is satisfactory. Theplasticizer may be mixed with the aniline prior to the heatingoperation, instead of after, if desired. The use of carbanilide,thiocarbanilide, and similar compounds that on heating can produceaniline or its homologs falls within the spirit of this invention. Theabove compounds may also be used as plasticizers.

In accordance with this invention, it has been discovered that rawnatural lignocellulose may be molded under heat and pressure in thepres-- ence of aniline. By natural lignocellulose is meant alignocellulose which has not been given a treatment which altersitchemically from its natural condition. The term includes a naturallignocellulose which has been comminuted and washed and dried. but notone which has been subjected to a chemical processing or digestion or tothe water-cooking operation described herein. Heretofore', it has beenunderstood that lignocellulose must be subjected to one of the ordinarymethods of hydrolysis, or to the water cooking operation describedheretofore, in order to be rendered sufliciently thermoplastic to enablethe production of hard, dense, water-resistant, resin-like products byhot-molding. In accordance with this invention, the aniline may be mixedwith the comminuted natural lignocellulose in an amount up toapproximately 15% of the lignocellulose, and the mixture subjecteddirectly to hot-molding, but preferably the'mixture is subjected to aheating operational; a temperature from 100 -C. to 225 C. prior to themolding operation, to fix the aniline. This provides the two-foldadvantage of conserving aniline and preventing the development of toxicaniline vapor during molding. A catalyst, such as described heretofore,may be added to the lignocelluloseaniline mixture before the heatingoperation to improve the fixation of the aniline. A lignin plasticizersuch as furfural and the phenols, or a mixture of two or more of suchplasticizers, may be added to the mixture before molding.

The natural lignocellulose is first comminuted to a size suitable formolding, and then preferably is washed with cold or hot water, and thendried. While the comminuted natural lignocellulose may be mixed withaniline and molded directly, as described heretofore, the washingoperation improves the molding properties of the product.

The washed natural lignocellulose is dried and mixed with the aniline,and then subjected directly to the hot-molding operation, or to theheating operation described heretofore, followed by molding. Thepresence of up to approximately 10% of water increases the plasticityduring molding.

The following are specific examples of methods of carrying out thepresent invention. It is understood that the examples are onlyillustrative and that additional modifications of the method may be madewithin the scope of the invention.

Example No. 1

Ash wood which has been comminuted to small particle size is cooked withan equal weight of water containing approximately 5% of caustic soda,based on the air dry weight of the wood, at a temperature ofapproximately 195 C. for one hour. Organic acids are freed from the woodduring the cooking, and the caustic soda is added for the purpose ofneutralizing these acids as they are liberated and making the masssubstantially neutral at the end of the cook. Any suitable alkalinematerial may be used, but an excess should be avoided. In accordancewith my copending joint application Serial No. 219,596, filed July 16.1938, the neutralization of the acids as they are liberated improves theplasticity and strength of the product. The cooked material is washedthoroughly with water to remove the substances which have been renderedwater soluble by the cooking operation, and is dried. It containssubstantially all of its natural lignin content in its natural locationon the cellulose. If it is not of a suitable fineness for molding, itmay be comminuted further. A particle size of 60 mesh per inch issuitable. The lignocellulose is then mixed with an aqueous solutioncontaining 0.1% copper sulphate, based on the weight of thelignocellulose, and is dried in an oven. It is then mixed withapproximately of aniline,

- and the mixture is heated for 1 hour at 170 C.

in a closed container. The resulting lignocellulose-aniline compositionis mixed with approximately 1% of zinc stearate and molded at atemperature of 180 C. and a pressure of 5000 pounds per square inch. Themodulus of rupture is 7250 pounds per square inch and the waterabsorption is 1.02% after being submerged in water at room temperaturefor 24 hours.

Example No. 2

Natural (unwashed) dry aspen wood is comminuted and mixed with 10% ofaniline and the mixture heated at 170 C. for one hour, and then moldedunder heat and pressure. The modulus of rupture is 8100 pounds persquare inch and the water absorption 10.8%.

Example No. 3

Natural hemlock sawdust is washed with water, dried at C., then mixedwith approximately 10% of aniline and heated at C. for one hour in aclosed container. The mixture is then mold- I ed under heat andpressure. The modulus of rupture is 7250 pounds per square inch and thewater absorption 2.70%.

Example No. 4

Natural ash wood is comminuted, washed and dried, then mixed with 10% ofaniline and heated at 170 C. for one hour in a closed container. Themixture is then molded under heat and pressure. The modulus of ruptureis 5200 pounds per square inch and the water absorption 2.30%.

Example No. 5

Natural white pine sawdust is washed with water and dried, and to it isadded 7 /2% of aniline and 5% of water with thorough mixing. The mixtureis molded (without preliminary heating) under heat and pressure. Themodulus of rupture is 6630 pounds per square inch and the waterabsorption 7.0%.

I claim:

1. The method of claim 10 in which the mixture is heated in a closedcontainer to prevent loss of aniline during heating.

2. The method of making a thermoplastic lignocellulose capable of beinghot-molded into a hard, resin-like product, which comprises cooking anatural lignocellulose with water at a temperature and pressuresufficient to render said lignocellulose thermoplastic, washing saidlignocellulose with water, drying said lignocellulose, mixing with saidlignocellulose approximately 1% to 15% of aniline, based on the weightof said lignocellulose, and a catalyst from the group consisting of theoxides and salts of vanadium, chromium, manganese, iron, cobalt, nickeland copper, and heating said mixture outside the mold at approximately100 C. to 225 C.

3. The method of making a thermoplastic lignocellulose capable of beinghot-molded into a hard, resin-like product, which comprises cooking anatural lignocellulose with water at a temperature and pressuresufiicient to render said lignocellulose thermoplastic, washing saidlignocellulose with water, drying said lignocellulose, making anintimate mixture consisting essentially of said lignocellulose andapproximately 1% to 15% of aniline, based on the weight of saidlignocellulose, and heating said mixture outside the mold at fromapproximately 100 C. to 225 C. and mixing with said heated mixture aplasticizer for lignin.

4. A thermoplastic composition having the property of plastic flow underheat and pressure cellulose and approximately 10% to 15% of anilinebased on the weight of said lignocellulose.

5. A thermoplastic composition having the property of plastic flow underheat and pressure molding conditions of 180 C. and 5000 pounds persquare inch respectively, with formation of hard, water-resistant,resin-like products, comprising a substantially moisture-free mixtureconsisting essentially of comminuted natural lignocellulose,approximately 1% to 5% of aniline, based on the weight of saidlignocellulose, and a catalyst from the group consisting of the oxidesand salts of vanadium, chromium, manganese, iron, cobalt, nickel andcopper.

6. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which comprises makingan intimate mixture consisting essentially of a natural lignocelluloseand approximately 1% to 15% of aniline, based on the weight of saidlignocellulose.

7. The method oi producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which comprises makingan intimate mixture consisting essentially of a natural lignocelluloseand approximately 1% to 15% of aniline and up to approximately of aplasticizer for lignin, based on the weight of said lignocellulose.

8. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which compriseswashing a natural lignocellulose with water, drying said washedlignocellulose and making an intimate mixture consisting essentially ofsaid dried lignocellulose and approximately 1% to of aniline, based onthe weight of said lignocellulose.

9. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which comprises makinga substantially moisture-free mixture consisting essentially of anatural lignocellulose. and approximately 1% to 15% of aniline, based onthe weight of said lignocellulose, and heating said mixture atapproximately 100 C. to 225 C.

10. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which compriseswashing a natural lignocellulose with water, drying said washedlignocellulose, making an intimate mixture consisting essentially ofsaid dried lignocellulose and approximately 1% to 15% of aniline basedon the weight of said lignocellulose, and heating said mixture atapproximately C. to 225 C.

11. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which comprises makinga substantially moisture-free mixture consisting essentially of anatural lignocellulose, approximately 1% to 15% of aniline, based on theweight of said lignocellulose, and a catalyst from the group consistingof the oxides and salts of vanadium, chromium, manganese, iron, cobalt,nickel and copper, and heating said mixture at approximately 100 C. to225 C'.

12'. The method of producing a thermoplastic lignocellulose capable ofbeing hot-molded into a hard, resin-like product, which comprises makinga substantially moisture-free mixture consisting essentially of alignocellulose containing substantially all of the lignin occurringnaturally therein and approximately 1% to 15% of aniline, based on theweight of said lignocellulose, and heating said mixture outside the moldat approximately 100 C. to 225 C.

13. The method of making a thermoplastic lignocellulose capable of beinghot-molded into a hard. resin-like product, which comprises cooking anatural lignocellulose with water at a temperature and pressuresuflicient to render said lignocellulose thermoplastic, water-washingand drying said lignocellulose, making an intimate mixture consistingessentially of said dried lignocellulose and approximately 1% to 15% ofaniline, based on the weight of said lignocellulose, and heating saidmixture outside the mold at approximately irom 100 C. to 225 C.

ARLIE W. SCHORGER.

CERTIFICATE OF CORRECTION. Patent no, 2,210,209. June 21;, 1941.

ARLIE w. SCHORGER.

It ie hereby ertified that error appears in the printed specificati onof the above numbered "patent requiring cerrection as follows: Page 3,first 601mm, 1 l 5, o "5% read 15%; and that the said Letters Patentshould be read with this correction therein that the sen: may conform tothe record of the ease in the Patent- Office.

Signed. and sealed thie 26th day of August, A. D. 19m.

7 Henry Van Aredale, (Seal) Acting Connniseiener of Patents.

